Decoding Tsinghua's big snow storm: A convergence of meteorological causes, regional vagaries and climate change
- Rick Dunham
- 12 minutes ago
- 4 min read
By MAO SHUJU
Global Business Journalism reporter
Beijing finally welcomed its first snow of the year on Dec. 12, nine days later than the city's average first-snow date of Dec 3. An unexpected heavy snow blanketed Tsinghua University in white, with snow accumulation on campus significantly thicker than in surrounding urban areas, providing ample material for Tsinghua students to freely sculpt artworks on the Zijing sports field.
Monitoring data from the Beijing Meteorological Observatory shows that "the precipitation at the Xierqi（西二旗） station in Haidian District reached 7.2 mm," ranking among the highest in the city. The snow, which started in the western mountainous areas in the early hours of Dec. 12, reached its peak intensity from noon until late evening.
On campus, the deepest snow accumulation was ankle-high, noticeably thicker than on the roads just a street away. Compared to previous years, this belated first snow not only covered the entire city but also far exceeded expectations in intensity. What exactly caused Tsinghua's snowfall to be heavier than other areas during the same period and compared to historical averages for the region?
Timing of the snowfall
By 6:00 a.m. on the 13th, "the city's average precipitation was 3.1 mm," but with significant regional variation. The precipitation recorded in the Xierqi area, where Tsinghua University is located, reached 7.2 mm, far exceeding the urban average of 4 mm. This figure was second only to the 7.9 mm recorded in Puwa（蒲洼）, Fangshan District, citywide. The snow's west-to-east progression meant western and northwestern areas were affected first, experiencing longer duration and greater intensity. Haidian District, being one of the first areas hit, naturally accumulated a thicker snow layer.
Topography and the urban heat island effect
Why did Tsinghua University become the "favored ground" for this heavy snow? According to a CNKI article, "topographic uplift is one of the decisive factors."
Tsinghua University is located in northwest Beijing, adjacent to the foothills of the Western Hills. When moisture-laden easterly or southeasterly winds blow toward Beijing, they first encounter the blocking effect of the Western Hills, forcing the air to rise. As the air ascends, it cools, causing water vapor to condense and leading to increased snowfall in western areas.
"It's like a natural 'snow-making machine,'" explained Li, a student in Tsinghua's meteorological science program. "Topographic forced uplift significantly enhances the snowfall efficiency in Tsinghua and its surrounding areas, resulting in greater snowfall per unit of time."
Simultaneously, the urban heat island effect played a significant role. Dense buildings and frequent human activities in the city center typically make temperatures 1-3 degrees Celsius higher than in suburban areas. This temperature difference likely caused snow to melt more easily upon landing in urban zones, while Tsinghua's relatively open green spaces and lower nighttime temperatures favored snow accumulation and preservation.
Large water bodies and vegetated areas on campus, such as lakes and lawns, also create a unique microclimate. Water bodies like the "Lotus Pond" release latent heat in winter, potentially increasing local air humidity and providing more abundant moisture conditions for snowfall.
The gift of atmospheric circulation
This year's first snow was not only late but also far more intense than in recent years. Meteorological data shows that the Beijing area experienced a prolonged lack of effective precipitation in the early winter of 2025, with no significant citywide snowfall occurring until early January.
In stark contrast to the early winter of 2024-2025, this snowfall event benefited from extremely favorable atmospheric conditions. Xin Xin, an analyst from China Meteorological Channel, pointed out, "This snowfall situation features ample moisture conditions, with both distant and nearby water sources." Long-distance moisture transport from the Bay of Bengal, combined with supplementary moisture from the nearby Bohai and Yellow Seas, provided a dual guarantee, bringing abundant moisture resources to the Beijing area.
Furthermore, the strength and timing of the cold air were ideal. Starting Dec. 10, a strong cold air mass moved from west to east across most of China, rapidly reversing the previously warm weather pattern. The encounter between this cold air and enhanced warm, moist airflows over Beijing created perfect conditions for snow. In contrast, during the winter of 2024, an abnormally westward position of the western Pacific subtropical high-pressure system was unfavorable for moisture transport to Beijing, leading to the delayed arrival of the first snow.
Signals of climate change
Extending the timeline reveals that this seemingly anomalous snowfall actually points to a broader climate picture. Data from the Beijing Climate Center shows that since January 1, 2025, the average temperature in Beijing's plain areas has been a full 1°C higher than the same period in previous years. This pattern of "initial warmth followed by sudden cold waves" makes the cooling process more drastic and the perceived temperature difference greater. Meteorological expert Zhao Wei explained, "After the cold wave outbreak, it didn't end quickly. Instead, weak cold air continuously replenished, preventing temperatures from rising effectively."
Against the backdrop of global warming, the increased frequency of extreme weather events is an indisputable fact, and the China Meteorological Administration has confirmed that China is currently experiencing a "La Niña" phenomenon. The occurrence of heavy snowfall against a warm winter background is a concrete manifestation of the complex impacts of climate change.
Preliminary analysis by Tsinghua University's climate research team suggests that with the reduction of Arctic sea ice and changes in jet streams, "delayed but intense" first-snow events like this year's may become more common in the future.
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